Possibly a 5.5 or 5.6? I'm not a professional though so don't follow my advice.
You'll need to Google images to see what you're looking for. Red in majirel terms will mean red though. What have you used previously?
Do lots of research and don't be tempted to go for a 4.* because it'll be darker than you think.
I'll post a picture of my colour so you can see how dark a 'light brown' actually is.
I've just copied this from a post that @TattyDevine posted a good few years ago that should help.
Here's a quick synopsis of how the Loreal colour numbering system works:
The first number relates to depth, or how dark the colour is from blonde to black.
10 Lightest Blonde
9 Very light Blonde
8 Light Blonde
7 Blonde
6 Dark Blonde
5 Light Brown
4 Brown
3 Dark Brown
2 Darkest Brown
1 Black
The second number relates to "tone". This is which tones are added to the depth to give you the finished effect for example copper or ash, so if you were to choose a base shade blonde (7) with gold tone added it would give you golden blonde.
•.1 = Blue ash
•.2 = Violet
•.3 = Gold
•.4 = Copper
•.5 = Mahogany
•.6 = Red
•.7 = Green ash
So Majirel 5.3 is Light Golden Brown. 116 in terms of Clairol is Natural Light Brown, and 116a is Natural Light Golden Brown. So you would be able to use Majirel 5.3 and be pretty pleased with the result, I would say.
I would be wary about doing your whole head with it if you've been dying your whole head - ideally you'd just "referesh" at the end by running it through in the last 10 minutes unless you have greys from root to tip. Do your roots then run it through at the end, I reckon.
You will need 20 volume (6 percent) developer (peroxide) and you need to mix the colour in the correct ratio. You use one and a half times the amount of developer to colour. So if you used 10ml of colour, you'd add 15ml of peroxide. If you wanted the kind of amount that you'd get in a box dye, measure out 50ml Majirel (its quite dense creamy stuff so 10 teaspoons, it doesn't "pour") and 75ml developer to make 125ml of made up dye. Let it sit for a few minutes to let the ammonia fumes evaporate a little.
I suggest anyone who wants to do professional dyeing at home reads all of the powerpoint presentations from this link to familiarise themselves with the products and numbering and procedure. That said, its not that different to box dye, but you want to get your colour right.
05/10/2011 07:25 TattyDevine
Just to add, as long as you have your colour right, Majirel will solve your grey coverage and colour fade issues. Its the dogs. Once its in, its in. That's why you should get your colour right!
If you put Majirel 5.3 into Google Images you should get a swatch book up which you can zoom in on. Ideally you'd go and look at one in a Sally's salon services or something.
Just to add, if you see colours with 2 numbers after the main number, that relates to secondary tone. So 5.31 is a light brown with a gold tone, but also some blue ash added to damnpen down that gold a bit and give a slightly more natural finish, 5.34 would be a much warmer tone because it would be a light golden brown with a copper undertone, 5.5 would be a mahogany brown, etc etc.